Dynamics of Wormlike Polymers in Solution: Self-Diffusion and Zero-Shear Viscosity

The dynamics of hairy-rod poly( p -phenylene)s in isotropic solutions are investigated by pulse field gradient NMR (PFG−NMR) and dynamic shear rheology for four different contour lengths over a broad concentration range. The self-diffusion coefficient, measured directly by PFG−NMR, and the longest relaxation time, determined by rheology, exhibit a significant slowing down with concentration, while the zero-shear viscosity increases. These dependencies are described successfully by predictions according to the fuzzy cylinder model and the “hole theory” considering the effect of the intermolecular hydrodynamic interactions. The entanglement effects are found to be stronger in the rotational motion and the zero-shear viscosity than in the translational motion and moreover to increase for shorter, more rodlike chains. The self-friction coefficient determined from PFG−NMR is found to differ from the cooperative friction measured by dynamic light scattering.